The present invention relates to a method and apparatus for producing an output signal having a high average power from a plurality of input signals wherein the high average power is achieved due to at least some of the input signals being phase shifted relative to one another.
In the prior art numerous systems and circuits are known for providing a transmittable signal formed from a plurality of carriers having different frequencies, such as tones in a telephone system, for example. One known approach is to use a plurality of transmitters, one for each carrier, which have their inputs connected to a common source having a standard frequency. Each of the transmitters has a different frequency derived from the standard frequency. The outputs of all the transmitters are connected to inputs of a combiner which then feeds an antenna. A disadvantage to this approach is that significant losses occur in the combiner which is typically a passive network. Also the use of multiple transmitters is costly.
Another approach in the prior art is to input all the input signals to one transmitter, however such a transmitter must handle the arithmetical sum of the peak voltages of all the input signals. This results in the use of expensive high power transmitters having a high peak to average power ratio.
The present invention overcomes these drawbacks in the prior art.